Inhibition of tumour necrosis factor and reversal of endotoxin-induced shock by U-83836E, a 'second generation' lazaroid in rats.

1. Antioxidants can exert protective effects in endotoxic shock by either a reduction of the oxidant damage or attenuation of Tumour Necrosis Factor (TNF-alpha) production. 2. Lazaroids are a family of compounds that inhibit lipid peroxidation. Besides, they can also reduce TNF-alpha. U-83836E is a new lazaroid lacking the glucocorticoid ring. 3. Aim of our study was to investigate the effect of U-83836E on TNF-alpha production either in vivo or in vitro. Endotoxic shock was produced in male rats by a single intravenous (i.v.) injection of 20 mg kg(-1) of S. enteritidis lipopolysaccharide (LPS). LPS administration reduced survival rate (0% survival, 72 h after endotoxin administration), decreased mean arterial blood pressure, increased serum and macrophage TNF-alpha and enhanced plasma malonylaldehyde (MAL) levels. Furthermore aortic rings from shocked rats showed a marked hyporeactivity to phenylephrine (PE 1 nM-10 microM). 4. Treatment with U-83836E (7.5, 15 and 30 mg kg(-1), i.v.) 5 min after endotoxin challenge significantly protected against LPS induced lethality (90% survival rate and 80% survival rate 24 h and 72 h after LPS injection respectively, following the highest dose of the drug), reduced hypotension, blunted plasma MAL, decreased serum and macrophage TNF-alpha and restored the hyporeactivity of aortic rings to control values. In vitro LPS stimulation (50 microg ml(-1) for 4 h) significantly increased cytokine production in macrophages (Mphi) harvested from untreated normal rats. Pretreatment with pertussis toxin (PT; 0.1, 1 and 10 ng ml(-1) 4 h before LPS) significantly increased TNF-alpha production. PT effects on these LPS responses were correlated with a PT mediated ADP ribosylation of a 41 kDa protein. U-83836E (50 microM) reduced, in a dose dependent manner, LPS induced TNF-alpha production and inhibited the PT effects on cytokine production and on ADP ribosylation of the protein. 5. Our data suggest that lazaroids may affect the early events associated with LPS receptor mediated activation of a G protein in LPS induced TNF-alpha production. These molecular events may explain, at least in part, the in vivo inhibition of cytokine production and reversal of endotoxic shock.